#define DAVINCI_I2C_TIMEOUT (1*HZ)
#define DAVINCI_I2C_MAX_TRIES 2
-#define I2C_DAVINCI_INTR_ALL (DAVINCI_I2C_IMR_AAS | \
- DAVINCI_I2C_IMR_SCD | \
+#define DAVINCI_I2C_OWN_ADDRESS 0x08
+#define I2C_DAVINCI_INTR_ALL (DAVINCI_I2C_IMR_SCD | \
DAVINCI_I2C_IMR_ARDY | \
DAVINCI_I2C_IMR_NACK | \
DAVINCI_I2C_IMR_AL)
u32 clkh;
u32 clkl;
u32 input_clock = clk_get_rate(dev->clk);
+ struct device_node *of_node = dev->dev->of_node;
/* NOTE: I2C Clock divider programming info
* As per I2C specs the following formulas provide prescaler
* where if PSC == 0, d = 7,
* if PSC == 1, d = 6
* if PSC > 1 , d = 5
+ *
+ * Note:
+ * d is always 6 on Keystone I2C controller
*/
- /* get minimum of 7 MHz clock, but max of 12 MHz */
- psc = (input_clock / 7000000) - 1;
+ /*
+ * Both Davinci and current Keystone User Guides recommend a value
+ * between 7MHz and 12MHz. In reality 7MHz module clock doesn't
+ * always produce enough margin between SDA and SCL transitions.
+ * Measurements show that the higher the module clock is, the
+ * bigger is the margin, providing more reliable communication.
+ * So we better target for 12MHz.
+ */
+ psc = (input_clock / 12000000) - 1;
if ((input_clock / (psc + 1)) > 12000000)
psc++; /* better to run under spec than over */
d = (psc >= 2) ? 5 : 7 - psc;
- clk = ((input_clock / (psc + 1)) / (pdata->bus_freq * 1000)) - (d << 1);
- clkh = clk >> 1;
- clkl = clk - clkh;
+ if (of_node && of_device_is_compatible(of_node, "ti,keystone-i2c"))
+ d = 6;
+
+ clk = ((input_clock / (psc + 1)) / (pdata->bus_freq * 1000));
+ /* Avoid driving the bus too fast because of rounding errors above */
+ if (input_clock / (psc + 1) / clk > pdata->bus_freq * 1000)
+ clk++;
+ /*
+ * According to I2C-BUS Spec 2.1, in FAST-MODE LOW period should be at
+ * least 1.3uS, which is not the case with 50% duty cycle. Driving HIGH
+ * to LOW ratio as 1 to 2 is more safe.
+ */
+ if (pdata->bus_freq > 100)
+ clkl = (clk << 1) / 3;
+ else
+ clkl = (clk >> 1);
+ /*
+ * It's not always possible to have 1 to 2 ratio when d=7, so fall back
+ * to minimal possible clkh in this case.
+ */
+ if (clk >= clkl + d) {
+ clkh = clk - clkl - d;
+ clkl -= d;
+ } else {
+ clkh = 0;
+ clkl = clk - (d << 1);
+ }
davinci_i2c_write_reg(dev, DAVINCI_I2C_PSC_REG, psc);
davinci_i2c_write_reg(dev, DAVINCI_I2C_CLKH_REG, clkh);
/* Respond at reserved "SMBus Host" slave address" (and zero);
* we seem to have no option to not respond...
*/
- davinci_i2c_write_reg(dev, DAVINCI_I2C_OAR_REG, 0x08);
+ davinci_i2c_write_reg(dev, DAVINCI_I2C_OAR_REG, DAVINCI_I2C_OWN_ADDRESS);
dev_dbg(dev->dev, "PSC = %d\n",
davinci_i2c_read_reg(dev, DAVINCI_I2C_PSC_REG));
/*
* Waiting for bus not busy
*/
-static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev,
- char allow_sleep)
+static int i2c_davinci_wait_bus_not_busy(struct davinci_i2c_dev *dev)
{
- unsigned long timeout;
- static u16 to_cnt;
-
- timeout = jiffies + dev->adapter.timeout;
- while (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG)
- & DAVINCI_I2C_STR_BB) {
- if (to_cnt <= DAVINCI_I2C_MAX_TRIES) {
- if (time_after(jiffies, timeout)) {
- dev_warn(dev->dev,
- "timeout waiting for bus ready\n");
- to_cnt++;
- return -ETIMEDOUT;
- } else {
- to_cnt = 0;
- i2c_recover_bus(&dev->adapter);
- }
- }
- if (allow_sleep)
- schedule_timeout(1);
- }
+ unsigned long timeout = jiffies + dev->adapter.timeout;
+
+ do {
+ if (!(davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB))
+ return 0;
+ schedule_timeout_uninterruptible(1);
+ } while (time_before_eq(jiffies, timeout));
+
+ dev_warn(dev->dev, "timeout waiting for bus ready\n");
+ i2c_recover_bus(&dev->adapter);
+
+ /*
+ * if bus is still "busy" here, it's most probably a HW problem like
+ * short-circuit
+ */
+ if (davinci_i2c_read_reg(dev, DAVINCI_I2C_STR_REG) & DAVINCI_I2C_STR_BB)
+ return -EIO;
return 0;
}
u16 w;
unsigned long time_left;
+ if (msg->addr == DAVINCI_I2C_OWN_ADDRESS) {
+ dev_warn(dev->dev, "transfer to own address aborted\n");
+ return -EADDRNOTAVAIL;
+ }
+
/* Introduce a delay, required for some boards (e.g Davinci EVM) */
if (pdata->bus_delay)
udelay(pdata->bus_delay);
dev_dbg(dev->dev, "%s: msgs: %d\n", __func__, num);
- ret = i2c_davinci_wait_bus_not_busy(dev, 1);
+ ret = i2c_davinci_wait_bus_not_busy(dev);
if (ret < 0) {
dev_warn(dev->dev, "timeout waiting for bus ready\n");
return ret;
static const struct of_device_id davinci_i2c_of_match[] = {
{.compatible = "ti,davinci-i2c", },
+ {.compatible = "ti,keystone-i2c", },
{},
};
MODULE_DEVICE_TABLE(of, davinci_i2c_of_match);
Code Review / kvmfornfv.git / blobdiff